R benchemoul



Jan' 24 1956 N. R. BENCHEMOUL ELECTRIC RELAYS' 0F THE LIQUID RESISTANCE TYPE 4 Sheets-Sheet l Filed Jan. 29, 1954 wwf w J E z/AAHLFlM/O *Mw/ u am# l 3 l N ,/0 y. a il MJ 9 f// T I ,MV l l w 7 a 2 4 w N @yf WQ E M Q TM om E M.,

Jan. 24, N' BENCHEMOUL ELECTRIC RELAYS OF THE LIQUID RESISTANCE TYPE Filed Jan. 29, 1954 4 Sheets-Sheet 2 Jan. 24, N R. BENCHEMOUL ELECTRIC RELAYS' OF THE LIQUID RESISTANCE TYPE Filed Jan. 29, 1954 4 Sheets-Sheet 3 ELECTRIC RELAYS OF' THE LIQUID RESISTANCE TYPE 4 Sheets-Sheet 4 Filed Jan. 29, 1954 Q f 6 /m m 6 l/M, n/ F 7 c 5 1/ 8 wf 6 N/f rHmHWH /M wv/ n; bwxj o6 Mn/) ,(7 v/76 7i( A MM E ,/46 a I Ud/I /7a 7 6 2 a 7 mw 7 H Q 8 d aan@ e M 78%8 1 9 'I 1 e 7 3 M lll|1|| ||l| ,/r/ w/ 1\ 4 G United States Patent O ELECTRIC RELAYS F THE LIQUID RESISTANCE TYPE Norbert R. Benchemoul, Paris, France Application January 29, 1954, Serial No. 407,!l26 Claims priority, application France January 29, 1953 16 Claims. (Cl. 26h-114) The present invention relates to an electric relay of the liquid resistance type, which is specially adapted for use as a circuit-breaker.

It is known that, when an increasing current is caused to pass between two electrodeswhich are enclosedwith-` in a chamber of small volume and which contains a conducting liquid communicating by means of long, narrow orifices with a reserve supply of liquid, an extremely rapid vaporisation of this liquid takes place as soon as a certain threshold value of current is exceeded.

This vaporisation is due to the accumulation of heat inside the small-capacity chamber, since this heat cannot be dissipiated by circulation of the liquid other than through the small orices previously referred to.

The present invention has for its object the use of the energy thus obtained in the form of vapour at a high pressure produced by reason of the small size of the oritices, which would allow it to escape and thereby to actuate a mechanical member serving to make or to break an electric current.

A liquid-resistance relay in accordance with the invention thus consists of a tank of small volume containing two electrodes and a conducting liquid, the said tank being in communication through narrow elongated orilices with a reservoir of variable volume of which one closure member is comprised by a movable wall carrying a mechanical member which is adapted to act as a means for opening or closing a contact member.

The contact member and the liquid resistance tank may be mounted in series, in such a way that the operation of the contact breaks the current passing through the tank and thus the apparatus operates as a circuit-breaker.

This constitutes an economic method of producing circuit-breaking apparatus which oiers the considerable advantage of ensuring, prior to the breaking of the current, for example in the case of a short-circuit, a considerable reduction in the current intensity which facil! itates the breaking of this same current by the contact member.

In the case of alternating current, the liquid resistance may with advantage be constituted by an electrolyte. In the case of direct current, if the current is permanently passed through the tank, there will be employed, on the contrary, a conducting liquid which is non-electrolytic, for example mercury. However, if the direct current is only passed through the tank of the relay in accordance with the invention in an accidental manner and only suficiently to ensure the vaporisation, an electrolyte may, in this case, also be used since the quantity of the electrolyte which is decomposed by theppassage of the current will then be very small.

The electrolytic solution utilised inside the tank may be constituted by highly-concentrated solutions of acids, salts or bases, so that their electric conductivity is high and, at the same time, they will be relatively unaffected, over very long periods, by slight differences in concentration or in temperature.

Electrolytes containing potassium ions will however be 2,732,460 Patented Jan. 24, 1956 f'ce preferred, such as for example aqueous solutions of caustic potash or of potassium carbonate, since experience shows that when the liquid is expelled from the tank due to the vaporisation of the said liquid, an electric arc does not tend to be produced between the electrodes when solutions of this kind are employed.

In one advantageous form of embodiment, the tank is housed within the interior of a vessel with which it communicates by means of the said long, narrow, small orifices, the said vessel containing a reserve supply of liquid and the wall of which is designed to radiate heat to the exterior.

Thus, in the case in which an electric current passes permanently through the tank, between the vessel and the said tank, there is set up a slight circulation of liquid by convection, which is however suicient in view of the low resistance of the liquid, for the dissipation of the heat generated; by varying the dimensions of the said orifices, and thereby varying the rate of circulation of the liquid, the value of the threshold current at which the vaporisation of the liquid inside the tank commences may be determined with precision. These small orifices prevent a too-rapid escape of the vapour and thereby permit the production of a high pressure of vapour, but nevertheless they do permit a partial escape of this contained vapour and thus prevent risk of explosion of the tank; furthermore, they also allow the -liquid to return to the'tank for a second operation.

However, if it is desired to obtain a powerful and rapid action of the contact member, these small communication oriiices may be provided with mechanical or dynamic clapper valves which normally permit the circulation of the liquid but which close, at least partially, at the moment at which the vapour is generated, so as to avoid a fall in pressure of the vapour inside the tank. In this case, there may be provided inside the tank a safety valve.

As the threshold of vaporisation of the liquid depends on the temperature of this liquid and, in addition, on the pressure to which the liquid is subjected, by the control of these two factors, it is possible to choose the operating point of the relay in accordance with the invention, in such a way that the said relay functions either as a thermostat -or as a pressostat (for automatic control of pressure). In this case,` the tank at least is made to Acommunicate with the zone of variable temperature or variable pressure so as to control the said zone.

The chamber of variable volume in which the vapour expands may be constituted lby a simple cylinder coacting with a piston. from .such a advantage.

ln order completely to avoid leakage of liquid, chambers having elastic walls may be employed such as bellows tubes.

The description which follows below in connection with the attached drawings, which is given by way of example only and not in any sense by way of limita tion, will makeit quite clear how the invention is to be carried into effect, the-specialfeatures which are referred to, either in the drawings or in the text, being understood to form a part of the said invention.

Fig. l is an axialA cross-section of a relay device in accordance with the invention, arranged as a circuitbreaker.

Fig. 2 shows an arrangement similar to that of Fig. l, being however slightly modified in order to permit an indication of an automatic opening action, if such is required. This gure is a cross-section along the line ll-II of Fig. 3.

Fig. 3 is a plan view of the arrangement shownv in Fig. 2 with the cover removed.

The risks of leakage of vapourlFig. 4 vshows the portion corresponding to the contacts of the arrangement .shown Yin ,Fig .2, .in .the `po-` sition of manual or automatic opening.

Fig. 5 shows an alternative form of embodiment of the liquidresistancettank =rin-cross=section.similar @to L'Fig. l and eFig. .2.

Fig. .6'is.a;cross-section of a circuit-"breaker -tor threephase .current Eig. :7 is aan .enlarged crossesection across the lines VII- VII of Fig. '6.

Eig. 5 shows ia .diagrammatic viewof'an arrangement by :means of lwhich the circu'itfbreaker'shown in Figs. 6 and i7 maybe transformed-into acontactor.

The 'arrangement-shown I.in Fig. 'l comprises acylindrica'lfyessel f1, for example "of 'sheet steel, :closed by .a base member 2 and containing the conducting liquid 3.

The liquidfiresistance tankliis "also vof cylindrical shape and is housed `inthe interiorofthevessel vv1 'and Ais carried on support which :is welded near 'to the bottom of .this vessel. Thisymetal "tan-k constitutes itself one of the electrodesand inside this tank, mounted concentrically .therewith,'there is arranged a second electrode 7 consisting-of a vsolid cylinder. The stwo electrodes are insulated and retained in vposition fwith respect to each other 'by means of :an 'insulating ring o which surrounds the tank f4 and in which the electrode? is tte'd.

The :vessel l'is closed by an yinsulating 'plate which istsupported with the interp'osition of :a flexible joint Si, both on an inwardly-hanged Vedge of the -vessel 1 and also .on the upper edge of the ring or tubular member 6. The holding-down bolts --10 ensure the vhermetic closure of the vessel 1.

The `electrode 7 isprOVide'd'with 'altairly large drilled hole .111 vparallel to its axis, fand this hole is extended yby a further .circular `passage '12 of 'smaller diameter, which gives .access tothe space 13 comprised between the'tank 4 and the electrode 7. -In the passage 11 is mounted a .piston 14 which is forced against the base of this passage by means of a spring "15. vThe sliding movement of the piston 14 inside'the .tubular hole 11 is guided by a rod 16 which is integral with the piston and which passes .through a threaded plug 17 which closes the upper extremity of the tubular hole 11.

.On the vrupper plate 3 and on the upper face of the electrode 7, there is mounted fa holloWed-out insulating block 18, vthe hollow central portion 18afo'f which houses the fixed contact studs 19 and l2t). 'The bolt 21 connects the :contact '19 to the 'electrode -7, whilst a conductor 22 passed in from the exterior, 'is -connec'ted'to the `contact 20. `The lconnection between the contacts is yeffected by means of van elasticfbridgetype blade 23 `which carries near its extremities the contactstuds 24 and 2S operating` respectively in conjunction vwith the 'studs 19 and 20.

The. springblade 23- is carried byl 'an insulating krod 26 to which it is iixed, on the one hand by means of a shouldered portion of this rod and also by a Cotterpin 27. The insulating rod passes into a drilled hole 28 in the block 18, this hole being co-axial with the drilled holes provided in the electrode 7, 'and its extremity is in the immediate vicinityof the top of the vrod 16 in the closed position of the contacts. The upper portion of the rod 26 is terminated by a AAbutton '26a'which is the on button. The rod A26 maybe'located in position by a ball 29, controlled lby a spring Sil-which abuts against a plug 31, `by virtue of the-grooves 32 and 33 which are provided in the said rod. A double-fork lever 34, pivotally'mounted about an axis l35, permits the rod 25 to be returned to its upper position after it has been depressed, by ymeans of an insulatingbutton 36 which constitutes the od button.

The arrangement which has just'been described func tions in the following mannerr' In the position shown in the figure, the current which passes in through thesconductor 22""goe's through the spring'blade 23 to arrive at the electrode '7 from which `it is .conducted .through Vthe .liquid .to .the Atank 4 and thence, through the support 5 of this tank, it may pass out through a terminal on the vessel 1, for example the terminal 37 to which is connected the outgoing conductor 38.

As long as the intensity `ofthe current remains at a normal value, -the current passes freely and the small ohmic losses `lin the tank are transmitted to the vessel 1 through the liquid which it contains and are radiated by this latter to the lexterior. vln addition, the tank 4 is provided with small orices of narrow and elongated lform, such as 39 and 40, which facilitate the dissipation oheat by permitting a small .amount .of circulation by convection of `the liquid in the electrolytic tank.

lf the currentintensity/increases abnormally, for example as a result of a short-circuit, the liquid contained in the space between the two electrodes is very rapidly vaporised -v(practically in a fraction of a cycle of the alternating current) and there results immediately atall in the intensity of the short-circuit'current, since r.the re sistance of the vapourof the liquid `to 'the passage of current is Vat least a hundred times greater than the resistance of the 'liquid'itsel 'Attire same time, thi's'vapour acts on the `piston 14- -and forces `this latter upwards, compressing the spring 15. The rod 26 is thereby pushed upwards and the contacts 19 and 24 on the one side, 'and 20 and 25 onthe other side, are opened.

It will furthermore be noted Vthat 'the electrical circuit forms 'a loop, and the arcs which'tend to 'be produced between the contact -studs are blown out'to the'right and to the left towards the 'exterior with 'respect 'to the lrod 26, 'and -this'avoi'ds'the formation "of "craters at 'the points of .contactof the studs.

The excess'vapourproduced in the utank passes through the orifices '39 and 'riti into the interior of the vessel where itcondenses and the Vliquid may once more return to the tank without diiculty, since the current is then cut-off at the point of the contacts. The interruption of -the current is maintained by the interlocking due to engagement of the lball 29 VVin the groove 33.

In order to prepare the device for further operation, it is'suicient to press the button 26awhic'h returns to the positionshown in the figure. Depression 'of the button 36 also enables ythe current passing through the circuit to be interruptedat will.

This device has, however, the disadvantage that it gives ino indication 'of the 'cause leading to the breaking of the circuit. It is, in fact, not possible to'nd out, in the first place, Whether (the contacts being open) the current has been broken by the action 'of the button 36 or by production of vapour.

-In order to remedy this disadvantage, the device may be modified in 'the marmer vshown "in Figs. 2 vand 3, thc conception of which is generally similar to that of the apparatus shown in Fig. 1.

On the insulating plate 8 which closes the vessel l, there is lmounted a U-shaped member 41 which serves as a support for the pivots 42 and 43. A blade 44 is arranged to pivot 'about the axis '42 'and one of the sides of this blade makes contact with the extremity ot the rod 16. On `the axis '43 the contact-'arm '4S is arranged to pivot and'this arm is connected at its lower extremity to the 'electrode 7 by means of a -flexible 'conductor 45 andthe bolt 21'. VThe contact-arm carries the stud 47 which cooperates with the xed stud '5'0 carried on a support 48 which is fixed to the insulating member 49. The incoming current conductor S1 is connected to the support 48.

yIn the contact-arm 45 there is housed a spring interlock, `the ball "52 of which projects from the rear face of the arm. In the bottom of the U-'shaped member 41. there is housed ya second spring interlock, the ball '53 of which projects from the bottom Vofthe U-'shaped member.

vThe apparatus is completed by three buttons, namely:

an onii button 54 and an off button 5.5, both of which slide in the insulating member 49 against the pressure of springs, and the operative ends of which are adapted to act on the contact-arm 4S on opposite sides of the pivot 43. The third button 56 which also slides against the pressure of a spring in the insulating block 57 xed between the extremities of the U-shaped member 41, is ar` ranged to act on the blade 44 beyond the pivotal axis of this latter.

The arrangement which has just been described operates in the following manner:

In the first place, as was the case in Fig. l, in the position shown in the figure, the current passes through the apparatus following the circuit formed by the conductor 51, the support 48, the studs 47 and 50, the contact-arm 45, the flexible conductor 46, the bolt 21, the electrode 7, the tank 4, the support 5 o this tank, the terminal 37 and the conductor 38.

In order to break the current deliberately, the button 55 is depressed, which pushes back the contact-arm 45- and forces the lower extremity of this latter to overcome the spring interlock provided by the ball 53.

Conversely, in order to place the apparatus again in circuit the button 54 is depressed, which causes the lower extremity of the arm 45 to pass over to the other side of the ball 53. As the upper portion of this arm is springy, the stud 47 is pressed against the stud 50 and this contact pressure is maintained by the ball 53. v

As can be seen with reference to Fig. 4 which shows the contact-arm 45 in the open position, the alternative and voluntary operation of the buttons 54 and 55 is not hindered by the blade 44, the upper extremity 44a of which remains in the vicinity of the pivot 43.

When the liquid in the tank is vaporised, the piston 14 is forced upwards and causes the blade 44 to pivot about its axis 42. During this movement, the upper extremity 44a of the blade forces the spring ball interlock 5,2 and by this means pushes back the arm 45 into the open position. During this movement, the blade 44 nally takes up the position 44 shown in Fig. 4, so that its extremity 44a, which has passed over to the other side of the ball 52, prevents the re-closing of thearm 4S by the button 54. ln order that the circuit may again be closed, it is necessary rst of all to depress the re-setting button 56 in order to force the extremity 44a of the blade 44 over to the other side of the ball 52. The arm 45 may then be re-set.

The necessity for depressing the button 56 before the contacts can be re-set gives an indication of the necessity of checking over the protected circuit in order to nd the cause which had led to the vaporisation of the liquid in the tank.

in the apparatus described, the needle valve of the piston 14, which closes the passage 12,-completes the air-tightness of the' vessel 1 in normal service, so that leakages of liquid out of this vessel are not likely to occur. When the circuit is opened as a result of the vaporisation, a very small quantity of vapour is able to escape into the spaces included between the piston 14 and the bore 11, and then between the rod 16 and its guide, but this quantity of vapour is negligible incomparison with the size of the reserve of electrolyte contained in the vessel 1. p interruptions may thus be obtained without causing any appreciable variation in the quantity of liquid contained in this vessel.

In the forms of embodiment described, it may happen that the vapour generated in the tank has not a suicient pressure to actuate the piston 14 because of the leakages of vapour which may take place through theorifices 39 and 40.

ln order to remedy this drawback, these orifices may be closed by clapper-valves, mechanically or aerodynamically operated, such as have been shown for example in Fig. 5.

A very large -nun'iber'of circuit.

In this iigure, the axes of the orices 3'9 are m'ade to converge towards each other in such a manner that, when vaporisation takes place, the two jets of vapour discharged from these orifices come into contact and cause a vortex movement in the vicinity of the outlet of the orifices 39, and this results in practice in a partial closing of these oriiices to the vapour which is discharged from them.

In this same ligure, the orice 40 is replaced by a drilled hole 60 in which is housed a small clapper valve 61, controlled by a restoring spring 62. A shouldered portion 61a of the rod of this clapper valve limits the travel of the latter. The plug 63 permits the clapper valve t0 slide whilst the small lateral channels 64 provide a communication between the tank 4 and the vessel in which it is contained when the clapper valve 61 is open. When the vaporisation occurs, the pressure rises within the interior of the tank 4 and the clapper valve 61 is forced against its seating.

Fig. 5 also shows a possible method of replacing the piston 14 by a bellows pipe element 65, the closed extremity of which is provided with a teat 65a which coacts with the rod 28. rEhe expansion of this bellows pipe is guided by the walls of the bore 11. Its open end rests on the bottom of this bore and may be for example, stuck to the bottom. The bellows pipe 65 communicates with the interior of the tank through the channel 12.

Thus, during normal operation, movement of the rod 28 is obtained by the expansion of the bellows without any loss of vapour and, in the event of excess pressure, this bellows acts as a safety valve since, if its expansion becomes too great, it may become unstuck from the bottom of the bore 11.

The circuit-breakers which have just been described may obviously be applied to the case of polyphase current, an electrolytic tank being inserted in each of the phases and the whole of the contacts being made integral with each other and carried by a common control member.

lt is an advantage to arrange all the tanks in one single vessel as shown in Fig. 6. in this vessel 66, there are xed hollow insulating blocks 67a, 671), 67e, in which are arranged the tanks 4a, 4b, 4c. The bottom of each of these tanks is provided with a rod (68a, 6819, 63e) which forms the outlet terminal of this tank. On the edge of the hollow blocks are supported the electrodes 7a, '7b. 7c inside the tanks. The pistons 14a, 1412, 14e, are mounted as in the previous examples in cylindrical holes drilled in these electrodes. rl`he whole assembly is covered over by an insulating plate 69 which serves as a cover-plate for the whole vessel, and which is provided with cavities 70a, 7Gb, 70e, in its lower portion which tit over the hollowed-out blocks on the base and press against the top face ofthe electrodes 7a, 7b, 7c. Each of the electrodes is connected through this base-plate to a contact stud 71a, 71b, 71e. On the upper face of this plate, are provided bearings 72 in which a shaft 73 is rotatably mounted and which, otherwise than at its bearing portions, is preferably of square cross-section and sheathed inside an insulating covering 74, as may be seen in Fig. 7.

At points opposite each of the rods of the'pistons 14a, 1`4b,14c, this shaft is provided with fingers 75a, 75b, 75C, and at points opposite each of the contact studs 71a, 71b, 71C, with contact arms, each of which is shaped as illustrated in Fig. 7 and comprises a spring blade 76 carried by a support 77 keyed to the shaft. At the opposite extremity of the blade 76 of the support 77, there is attached a exible conductor 78 which ends in the incoming current terminal 79.

On the shaft 73, there is, in addition, mounted a seg ment 80 provided with two circular notches 81 and 82 with which engages a ball 83 controlled by a restoring spring 84 which is carried on a support 85 xed to the -7 plate k69; this-support is partly ofthe sameshapeasthe segment 80.

Finally, at the end `of the shaft vis ixed a handle 87 by means of which it 'may be .rotated manually.

In normal operation, theliquid contained in the vessel 6o serves asa common reservoir forv'all-the tanks. There is no disadvantagein this since,due tothe relative insulation of these tanks, leakages of current are not likely to occur in the liquid, except through the crice's which are formed in the said 'tanks to .provide a communication between .them and the interior-of the vessel 66.

The insulation -thus obtainedmay be-still lfurther irnproved by arranging these orifices in the form `of small elbowedtubes 8S, preferablyof insulating material, which have the further advantage by `reason vof ktheir lelbowed form, of constituting aerodynamicfclapper-valves incase of vaporisation `inside the tanks. it Ais known, in fact, that any rapid Aow is reduced by the elbowed tubes. Furthermore, by suitably choosing the length -of these small tubes, circulation of 'the liquid in the tanks under steady conditions may be controlled.

The operation of this embodiment is similar to that of the forms Vor" embodiment described vitith reference to Figs. l and. 2. When one of the pistons ldpu'shes away the corresponding finger 75, the shaft 73 'rocks asa whole and the interlock effected by the ball 33, which previously maintained the shaft in the position atV which the contacts were closed, now lmaintains it in the position with contacts open. The re-closing of the contacts is carried out by hand, by means of the handle 87.

'In the embodiments described, the contacts which are actuated by the pressure of vapour are mounted in series with the tank. The contacts and the tank may also be connected to two independent circuits whereby one circuit may control the other. The device then constitutes eithera maximum voltage or a maximum current relay for the current which passes through the tank. Following the arrangement of the contacts, either the opening or the closing of the circuit controlled may be effected in the case of actuation by vapour pressure. Nevertheless, the circuit passing through the tank is preferably controlled by an auxiliary contact actuated by the vaporisation of the liquid in the tank, in order that the amount of liquid vaporised shall always be limited.

in particular, the arrangement shown in Fig. 8 enables the circuit-breaker shown in Figs. 6 and 7 to be converted into a true contactor which is 'adapted to be operated from a distant point.

To this end, the handle 87 is replaced by a balance-arm S9, the extremities 89a and 89b of which are adapted to co-opcrate with rods 90a and Sub which can be actuated (in the same way as the rods of the pistons i6 of Figs. l and 2 or the bellows ,pipes 65 of Fig. 5), by liquidresistance tanks 91a and 9th which may be Aenclosed in a common vessel, shown diagrammatically by the outline in chain-dots 92. A separate source of direct or alternating current represented by the terminals 93, supplies the two tanks'in parallel through the intermediary ot the push-buttons 94 and 95, of which one constitutes the on button and the other the oit button. In -addition, on the shaft 73 are Xed auxiliary contacts 97 and 9S which are operated by -the rotation of the said shaft, in such a way that one of the contacts is open and the other closed and vice-versa, when the shaft 73 is in one or the other of its interlocked positions.

in Fig. 8, this result is 'obtained by means of a small auxiliary balance-arm made up ofthe arms 99a and 99h to which the auxiliary contacts -are connected.

ifit is supposed that Fig. 8 corresponds to ifig. 7'in the position shown in 'full lines of the arm S9, the main contacts are closed and so is also the contact 97. On depressing the button lQS '(thebi button) the :rod 99a is forced outwardsland rotates the vshaft 73 which opens the main contacts and, at the Sametime, opens the contact 97 and closes 'the Contact 9S. The balancearm S9v then passes to `the position shown in 4'dotted lines and the maincontactsareopen.

llt willfbe noted that, Ias-soon as the vaporisation'in the tank `91a has `become .suiicient Afor Athe movement of the rod a -to be transmitted to the shaft, this vaporisation has beenstoppedbyrtheopeningof the contact 97. Furthermore, the-rod 90a returns -to itsposition as soon as the vapourha-s'condensed. It is easy to see that a pressure on the button 94 under the same conditions causes the balance-arm 89 lto ,pass `from its dotted-line position to its full-line position and thus ensures the closing ofthe main-contacts.

`An apparatus vconstructed -in this way thus constitutes a complete Vcontacter circuitsbreaker.

It will be clearly understood that modiicationsmay be made .to the relays which have just been described above, in ,particular by `the Asubstitution of equivalent technical means, withoutthereby 'departing Ifrom the spirit or from thescope ofthe lpresent invention.

What I claim is: y

v1.7An electricrrelaycomprising a liquid-resistance cell having two closely-spaced electrodes with opposite surfaces'boundinga narrow compartment, a vaporizable conductiveliquid-insidesaid electrodes for passing electrical energy from the terminals, through the conductive liquid, when `voltage is 'applied to said terminals; a vessel containing a reserve supply of `said conductive liquid; passage means for connecting said vessel with said compartment, said .passage meansbeing designed for oiering substantial resistance to flow `therethrough at least in the direction of ow from saidcompartment to said vessel; a chamberof variable volume having a movable wall element and communicating with said compartment; an electric circuit; `switching means in said circuit, having at leastone contact; and contact control means, operatively associated with said movable wall element, for yopening and closing said electriccircuit in response to a displacement of said wall element.

2. The rela'yac'cording to claim l, further comprising resilient locking 'means lfor maintaining the contact controlmea'ns in opening position and in closing position.

3. The relay according to claim l, further comprising external means for'operating the contact control means.

4. The relay according to claim l, wherein the cornpartment is bounded by the electrodes.

5. The relay according to claim l, comprising valve means, responsive to pressure of vapor generated in the cell, for obtu'rating the passage means, at least partly.

6. The relay `according to claim l, wherein the charnber or variable volume comprises a cylinder and a piston therein, saidfpiston constituting the movable wall element associated with the contact control means.

7. The relay according to claim 6, wherein thepiston comprises Van end shaped as a needle valve and cooperating'with a valve seat formed on the communication bctween the compartment and the cylinder.

8. The relay according to claim 4, wherein the cell comprises a hollow cylinder of conductive material forming one electrode, a cylindrical electrode inside, spaced from and generally coaxial with said hollow cylinder, and an insulating annular connecting member between said hollow cylinder and said cylindrical electrode, said member being adapted to close the annular space bounded by said electrodes. v

9. The relay 'according to claim 8, wherein the chamber of variable volume comprises a cylinder bored in Vthe cylindrical electrode and apiston in said cylinder, said piston constituting the movable wall element associated with the contact control means.

l0. Therelayfaccording lto claim Vl, wherein the 4liquidresistance cell and the contact control means are arranged in series relation whereby the relay operates as a cutoff device.

il. The relay acldig fo `llilr-l 1, Whfe'iriti-'iVi-t'ching means comprises two contact studs, and the Contact control means comprises a bridging member extending between said studs and movable generally perpendicularly to the line passing through said studs.

12. The relay according to claim 11, further comprising two push-buttons adapted to alternatively control the contact control member to open and close the circuit.

13. The relay according to claim 1, comprising a swingable member adapted to operatively associate the contact control means with the movable wall element, and resilient locking means for maintaining said swingable member in the positions thereof corresponding to opening and closing of the circuit.

14. The relay according to claim 13, wherein the contact-control means includes a pivotal lever, and further comprising resilient locking means for maintaining said lever in opening position and in closing position, and two push-buttons operatively associated with said lever and arranged on both sides of the pivotal axis thereof.

15. The relay according to claim 1, wherein the electric circuit is a multiple-phase circuit with independent contacts in each phase, and comprising a liquid-resistance cell arranged in series relation with each phase, the movable wall elements associated with the various cells cooperating with a common contact control means related to said contacts.

16. The relay according to claim l, wherein the liquidresistance cell and the contact control means belong to different electric circuits.

References Cited in the tile of this patent UNITED STATES PATENTS 1,316,095 Illingworth Sept. 16, 1919 1,490,925 Illingworth Apr. 22, 1924 2,169,857 Treanor Aug. 15, 1939 2,291,163 Kraeuter July 28, 1942 2,553,291 Barr May l5, 1951 2,619,566 Mahoney Nov. 25, 1952 

